The epidermis undergoes striking morphologic and biochemical changes in the course of maturation of the basal cell to the dead squame of the stratum corneum. The factors controlling the orderly progression of the events are largely unknown. This proposal seeks to determine whether membrane essential fatty acids (FAs) are critical for maintaining normal epidermal biology, and whether alterations in keratinocyte membrane FA constituents can induce a transition from the proliferative to the differentiative state. We will analyze the membrane FA composition of mouse keratinocytes cultivated under conditions which favor either continued proliferation or terminal differentiation. In a parallel approach, we will cultivate keratinocytes in lipid-free media enriched with specific FAs, and correlate morphologic and biochemical markers of differentiation and proliferation to the FA membrane composition. In this way we will be able to determine which FAs can induce differentiation and which proliferation. The PI candidate has worked previously investigating the modulation of keratinocyte plasminogen activator (PA) in differentiating mouse keratinocytes. She has become proficient in keratinocyte culture and in the techniques of evaluating keratinocyte differentiation. These include quantification of squame formation and nuclear dissolution, PAGE analysis of keratins, immunofluorescent analysis of keratinous cytoskeleton, and assays of cell-associated PA activity. Many of the proposed studies will be carried out in the laboratory of Dr. Vincent A. Ziboh, a lipid and prostaglandin biochemist of world repute, whose work has elucidated the pathways of lipid metabolism and prostaglandin biosynthesis in the skin.